Catalysts for the oxidation of olefins to unsaturated aldehydes

ABSTRACT

Catalysts are provided which are useful in the oxidation of olefins to aldehydes and conjugated dienes and in ammoxidation of olefins to nitriles. The catalysts comprise the combined oxides of uranium and arsenic on a catalyst support and the combined oxides of uranium and arsenic promoted by molybdenum, boron, vanadium, tin, nickel, bismuth, chromium, iron, manganese, zinc, tungsten, antimony, cerium, cobalt or rhenium.

United States Patent Grasselli et al..

CATALYSTS FOR THE OXIDATION OF OLEFINS TO UNSATURATED ALDEI-IYDES Inventors: Robert K. Grasselli, Chagrin Falls;

Maria S. Friedrich, Cleveland, both of Ohio Assignee: Standard Oil Company, Cleveland,

Ohio

Filed: Dec. 7, 1971 Appl. No.: 205,706

Related U.S. Application Data Continuation-impart of Ser. No. 16,984, March 5, 1970, which is a continuation of Ser. No. 691,992, Dec. 20, 1967, Pat. No. 3,544,616.

U.S. Cl. 252/432; 252/456; 252/458;

260/604 R Int. Cl. BOlj 11/82; BOlj ll/O6 Field of Search 252/456, 458, 432, 467;

[ 1 June 17, 1975 [56] References Cited UNITED STATES PATENTS 3,293,280 12/1966 Young et al. 252/467 X 3,308,15l 3/1967 Callahan et al.... 252/467 X 3,431,292 3/1969 Callahan et al 252/456 X Primary Examiner-C. Dees Attorney, Agent, or Firm-Herbert D. Knudsen 5 7] ABSTRACT vanadium, tin, nickel, bismuth, chromium, iron, manganese, zinc, tungsten, antimony, cerium, cobalt or rhenium.

4 Claims, No Drawings CATALYSTS FOR THE OXIDATION OF OLEFINS TO UNSATURATED ALDEHYDES CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation-impart of our copending US. Pat. application Ser. No. 16,984 filed Mar. 5, 1970, which is a continuation of U.S. patent application Ser. No. 691,992 filed Dec. 20, 1967, now US. Pat. No. 3,544,616.

BACKGROUND OF THE INVENTION This invention relates to oxidation catalysts comprising oxides of uranium and arsenic optionally incorporating promoters, which are useful for the catalytic oxidation of olefins to aldehydes and conjugated dienes, and for the catalytic ammoxidation of olefins to nitriles. The catalytic oxidation reactions are exemplified by the oxidation of propylene to acrolein, the oxidation of isobutylene to methacrolein, the oxydehydrogenation of an olefin having 4 to 8 carbons, such as the oxydehydrogenation of butene-l or butene-2 to butadiene-1,3, the ammoxidation of propylene to acrylonitrile and the ammoxidation of isobutylene to methacrylonitrile.

The prior art is replete with a multiplicity of oxidation catalysts particularly suited to the same reactions disclosed herein. Some of these oxidation catalysts are disclosed in US. Pat. Nos. 2,904,580; 3,142,697; 3,179,694; 3,197,419; 3,198,750; 3,260,081; 3,200,084; 3,226,421; 3,248,340; 3,264,225; 3,251,900; 3,257,474; 3,260,768; French Pat. Nos. 1,255,121; 2,269,382; and British Pat. Nos. 864,666; 876,446; 983,755. It is well-known that some catalysts are more successful than others and that the search for economically competitive catalysts continues unremittingly. The oxidation catalyst of the instant invention is a superior catalyst.

DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION The uranium oxide-arsenic oxide base catalyst disclosed herein is referred to as a mixture of uranium and arsenic oxides, but this is not to be construed as meaning that the catalyst is composed either in whole or in part of only these compounds. The proportions of arsenic and uranium in the catalyst system may vary widely. The preferred uranium:arsenic atomic ratio ranges from about 25:1 to about 1:6; optimum activity appears to be obtained at uraniumzarsenic atomic ratios within the range of from about 1:1 to about 1:4 and the catalyst is characterized by a negligible loss of arsenic despite the relatively high reaction temperatures of the catalytic processes in which it is useful.

The catalyst of the instant invention contains from to 95 percent by weight of a catalyst support, and preferably between 10 and 90 percent. Any known catalyst support such as alumina, pumice, silicon carbide, titania, zirconia, alumina-silica, and the inorganic phosphates, silicates, aluminates, borates and carbonates stable under the reaction conditions, may be used but silica is preferred.

1n the preparation of the base catalyst useful in this invention, the arsenic oxide and uranium oxide can be blended together or can be formed separately and then blended or formed separately, or together in situ.

The uranium oxide component of the instant catalyst can be useful in the form of uranous. uranic or combined uranous-uranic oxides, or by precipitation in situ from a soluble uranyl salt, such as the nitrate, acetate, or a halide such as the chloride. Uranium metal can be used as a starting material, and if free arsenic is also employed, the arsenic can be converted to the oxide and the uranium to the nitrate simultaneously by oxidation in hot nitric acid. A slurry of hydrous arsenicarsenic oxide in nitric acid can be combined with a solution of a uranium salt which is then precipitated in situ as the hydroxide by making the solution alkaline with ammonium hydroxide, the ammonium nitrate and the other ammonium salts being removed by filtration of the resulting slurry or by thermal decomposition.

It will be apparent from the above that uranous and uranic bromides, chlorides, fluorides and iodides, nitrates, acetates, sulfites, sulfates, phosphates, thiocyanates, thiosulfates, oxalates, formates and hydroxides can be employed as the source of the uranium oxide components. A preferred souce is uranyl nitrate.

As starting materials for the arsenic oxide component there can be used any arsenic oxide such as arsenic thioxide or arsenic pentoxide; or a hydrolyzable or decomposable arsenic salt such as an arsenic halide. Arsenic metal can be employed, the oxide being formed by oxidizing the metal with an oxidizing acid, such as nitric acid. A preferred starting material is orthoarsenic acid.

The catalytic activity of the novel catalyst embodied in the present invention, is enhanced by heating the catalyst at an elevated temperature. Preferably, the catalyst mixture is dried and heated at a temperature of from 500 to 1,500F, more preferably at about 700 to 900F for from 2 to 24 hours. If activity then is insufficient, the catalyst can be further heated at a temperature above about 1,000F but below a temperature deleterious to the catalyst at which it is melted or decomposed, preferably from about 1,100F to about 1,800F for from 1 to 48 hours, in the presence of oxygen or an oxygen-containing gas such as air.

In general the higher the activation temperature, the less time required to effect activation. The sufficiency of activation at any given set of conditions is ascertained by a spot test of a sample of the material for catalytic activity. Activation is best carried out in an open chamber, permitting circulation of air or oxygen, so that any oxygen consumed will be replaced.

The instant catalyst comprising the combined oxides of uranium and arsenic may be defined by the following empirical formula U, As O where the As:U atomic ratio is in the range from about 1:25 to about 10:1 and z is determined by the oxidation state of U and As in the catalyst. It is conjectured that the combined oxides of the instant catalyst are present as an activated catalytic oxide complex.

Various metal oxides have been found to act as promoters in conjunction with the uranium-arsenic base catalyst, as for example, minor amounts of an element or elements selected from Groups I-A, I-B, II-A, II-B, 1ll-B, lV-A, IV-B, V-B, VI-B, VII-B, and VIII of the Periodic Table. Particularly effective promoters are the oxides of molybdenum, boron, vanadium, tin, nickel, bismuth, chromium, iron, manganese, zinc, antimony, cerium, and tungsten in an amount corresponding to less than one atomic equivalent per atomic equivalent of either uranium or arsenic.

Promoter oxides may be incorporated into the base catalyst by blending into the gel before calcining, or by blending into the oven-dried base catalyst before calcining. A preferred manner of incorporating promoter elements is by choosing a water-soluble salt of the promoter element, forming an aqueous solution of the salt, and mixing this solution with uranyl nitrate and orthoarsenic acid solutions, and stirring while continuously heating till the solution gels. The gel is then spooned into trays and oven-dried at 120C overnight. The dried catalyst is then calcined starting at 800F, the temperature raised to 900F over a period of 2 hours and the catalyst calcined overnight at this temperature. A further calcination at a higher temperature of at least 1,000F for 3 hours is generally employed to increase the activity of the catalyst complex. This catalyst system is useful in the oxidation of olefins to oxygenated compounds, such as aldehydes and acids, in the presence of oxygen; in the oxidation of olefins to unsaturated nitriles in the presence of oxygen and ammonia; and in the oxydehydrogenation of olefins to diolefin and aromatic compounds. Nitriles and oxygenated compounds such as aldehydes and acids can be produced simultaneously using process conditions within the overlapping ranges for these reactions as set forth in detail below. The relative proportions of each that are obtainable will depend on the process conditions, the particular catalyst and on the olefin. The same catalyst may produce predominantly the nitrile with propylene and predominantly the aldehyde and/or acid with isobutylene. The term oxidation as used in this specification and claims encompasses the oxidation to aldehydes and acids and to nitriles and dienes all of which oxidation reactions require oxygen as a reactant.

OXIDATION OF OLEFINS TO ALDEHYDES AND ACIDS The reactants used in the oxidation to oxygenated compounds are oxygen and an olefin having only three carbon atoms and a straight chain such as propylene or isobutylene or mixtures thereof.

The olefins may be in admixture with pa'raffinic hydrocarbons, such as ethane, propane, butane, and pentane; for example, a propylenepropane mixture may constitute the feed. This makes it possible to use ordinary refinery streams without special preparation.

The temperature at which this oxidation is conducted may vary considerably depending upon the catalyst, the particular olefin being oxidized and the correlated conditions of the rate of throughput or contact time and the ratio ofolefin to oxygen. In general, when operating at pressures near atmospheric, i.e., l to 100 psig, temperatures in the range of 500 to 1,100F may be advantageously employed. However, the process may be conducted at other pressures, and in the case where superatmospheric pressures, e.g., above 100 psig, are employed. somewhat lower temperatures are possible. In the case where this process is employed to convert propylene to acrolein, a temperature range of 750 to 950F has been found to be optimum at atmospheric pressure.

While pressures other than atmospheric may be employed, it is generally preferred to operate at or near atmospheric pressure, since the reaction proceeds well at such pressures and the use of expensive high pressure equipment is avoided.

The apparent contact time employed in the process is not critical and it may be selected from a broad operable range which may vary from 0.1 to 50 seconds. The apparent contact time may be defined as the length of time in seconds which the unit volume of gas measured under the conditions of reaction is in contact with the apparent unit volume of the catalyst. It may be calculated, for example, from the apparent volume of the catalyst bed, the average temperature and pressure of the reactor, and the flow rates of the several components of the reaction mixture.

The optimum contact time will, of course, vary depending upon the olefin being treated, but in the case of propylene and isobutylene, the preferred apparent contact time is 0.15 to 15 seconds.

A molar ratio of oxygen to olefin between about 0.5:1 to 5:1 generally gives the most satisfactory results. For the conversion of propylene to acroelin, a preferred ratio of oxygen to olefin is from about 1:1 to about 2:1. The oxygen used in the process may be derived from any source; however, air is the least expensive source of oxygen and is preferred for that reason.

Water is formed as a product of reaction and it has been found that it has a beneficial influence on the course of the reaction in that it improves the conversion and the yields of the desired product. Sometimes it is desirable to add some water to the reaction mixture. The manner in which water affects the reaction is not fully understood but the theory of this phenomenon is not deemed important in view of the experimental results we have obtained.

Inert diluents, such as nitrogen and carbon dioxide, may be present in the reaction mixture.

OXIDATION OF OLEFINS TO NITRILES The reactants are the same as those used in the oxidation of olefins to aldehydes described above except that ammonia is included as a reactant. Any of the olefins described above can be used.

In its preferred aspect, the process comprises contacting a mixture comprising propylene or isobutylene, ammonia and oxygen with either the promoted or unpromoted catalyst of this invention at an elevated temperature and at atmospheric or near atmospheric pressure.

Any source of oxygen may be employed in this process. For economic reasons, however, it is preferred that air be employed as the source of oxygen. From a purely technical viewpoint, relatively pure molecular oxygen will give equivalent results. The molar ratio of oxygen to the olefin in the feed to the reaction vessel should be in the range of 0.521 to 4:1 and a ratio of about 1:1 to 3:1 is preferred.

Low molecular weight saturated hydrocarbons do not appear to influence the reaction to an appreciable degree, and these materials can be present; consequently the addition of saturated hydrocarbons to the feed to the reaction is contemplated within the scope of this invention. Likewise, diluents, such as nitrogen and the oxides of carbon, may be present in the reaction mixture without deleterious effect.

The molar ratio of ammonia to olefin in the feed to the reactor may vary between about 0.05:1 to 5:1. There is no real upper limit for the ammoniaiolefin ratio, but there is generally no reason to exceed the 5:1 ratio. At ammoniazolefin ratios appreciably less than the stoichiometric ratio of 1:1, various amounts of oxygenated derivatives of the olefin will be formed.

Significant amounts of unsaturated aldehydes, as well as nitriles, will be obtained at ammoniarolefin ratios substantially below 111, i.e., in the range of 0.15:1 to

0.75:1. Outside the uppper limit of this range only insignificant amounts of aldehydes will be produced, and only very small amounts of nitriles will be produced at ammoniazolefin ratios below the lower limit of this range. It is fortuitous that within the ammoniazolefin range stated, maximum utilization of ammonia is ob tained and this is highly desirable. It is generally possible to recycle any unreacted olefin and unconverted ammonia.

A particularly surprising aspect of this invention is the effect of water on the course of the reaction. We have found that in many cases water in the mixture fed to the reaction vessel improves the selectivity of the reaction and the yield of nitrile. However, reactions not including water in the feed are not to be excluded from this invention inasmuch as water is formed in the course of the reaction.

In general, the molar ratio of added water to olefin, when water is added, is at least about 0.25: l. Ratios on the order of 1:1 to 3:1 are particularly desirable, but higher ratios may be employed, i.e., up to about :1.

The reaction is carried out at a temperature within the range of from about 550 to l,l00F. The preferred temperature range is from about 800 to 1,000F.

The pressure at which the reaction is conducted is also an important variable, and the reaction should be carried out at about atmospheric or slightly above atmospheric (2 to 3 atmospheres) pressure. In general, high pressures, i.e., about 250 psig, are not suitable, since higher pressures tend to favor the formation of undesirable by-products.

The apparent contact time is not critical, and contact times in the range of from 0.1 to about 50 seconds may be employed. The optimum contact time will, of course, vary depending upon the olefin being treated, but in general, a contact time of from 1 to seconds is preferred.

THE OXIDATIVE DEHYDROGENATION OF OLEFINS TO DIOLEFINS AND AROMATICS In accordance with the present invention, the promoted or unpromoted catalyst system is employed in the catalytic oxidative dehydrogenation of olefins to diolefins and aromatic compounds. In the process, the feed stream in vapor form containing the olefin to be dehydrogenated and oxygen is conducted over the promoted catalyst at a comparatively low temperature to obtain the corresponding diolefin or aromatic compound.

By the term olefin as used herein is meant the open chain as well as cyclic olefins. The olefins dehydrogenated in accordance with this invention have at least four and up to about eight non-quaternary carbon atoms, of which at least four are arranged in series in a straight chain or ring. The olefins preferably are ei ther normal straight chain or tertiary olefins. Both cis and trans isomers, where they exist. can be dehydrogenated.

Among the many olefinic compounds which can be dehydrogcnated in this way are butene-l; butene-Z', pentene-l; pentcne-Z; heptene-l; octene-l; tertiary pentenes and hexencs having one tertiary carbon atom such as Z'methyl-pentene-l, 3-methyl-butene-l, 3,4-dimethyl-pentene-l. 4-methyl-pentene-2; other branched chain olefins such as Z-methyl-butene-Z, 2- methyl-butene-l. R-methyl-pentene-Z; cyclo-olefins such as cyclopentene; cyclohexene; 3-methyl cyclohexene and cycloheptene.

Open chain olefins yield diolefins, and, in general, six-membered ring olefins yield aromatic ring compounds. The higher molecular weight open chain olefins may cyclize to aromatic ring compounds.

The feed stock in addition to the olefin and oxygen can contain one or more paraffinic or naphthenic hydrocarbons having up to about 10 carbon atoms, which may be present as impurities in some petroleum hydrocarbon stocks and which may also be dehydrogenated in some cases. In this oxidative dehydrogenation reaction. propylene and isobutylene should not be included in the feed in substantial amounts.

The amount of oxygen should be within the range of from about 0.3 to about 3 moles per mole of olefin. Stoichiometrically, 0.5 to 1.5 moles of oxygen per mole of olefin is required for the dehydrogenation to diolefins and aromatics respectively. It is preferred to employ an excess of oxygen, from 1 to about 2 moles per mole of olefin, in order to ensure a higher yield of diolefin per pass. The oxygen can be supplied as pure or substantially pure oxygen or as air or in the form of hydrogen peroxide.

When pure oxygen is used, it may be desirable to incorporate a diluent in the mixture such as steam, carbon dioxide or nitrogen.

The feed stock is preferably catalytically dehydrogenated in the presence of steam, but this is not essential. Usually, from about 0.1 to about 6 moles of steam per mole of olefin reactant is employed, but amounts larger than this can be used.

The dehydrogenation proceeds at temperatures within the range of from about 325C to about l,000C. Optimum yields are obtainable at temperatures within the range from about 400 to 550C. However, since the reaction is exothermic, temperatures in excess of 550C should not be used, unless means are provided to carry off the heat liberated in the course of the reaction. Due to the exothermic nature of the reaction, the temperature of the gaseous reaction mixture will be higher than the temperature of the feed entering the system by as much as C. The temperatures referred to are those of the entering gas feed near the reactor inlet.

The preferred reaction pressure is approximately atmospheric, within the range of from about 5 to about 75 psig. Higher pressures up to about 300 psig can be used and have the advantage of simplifying the product recovery.

Only a brief contact time with the catalyst is required for effective dehydrogenation. The apparent contact time with the catalyst can vary from about 0.5 up to about 50 seconds but higher contact times can be used if desired. At these contact times, comparatively small reactors and small amounts of catalyst can be used effectively.

In general, any apparatus of the type suitable for carrying out oxidation reactions in the vapor phase may be employed in the execution of these processes. The processes may be conducted either continuously or intermittently. The catalyst bed may be a fixed bed employing a large particulate or pelleted catalyst or, in the alternative, a so-called fluidized bed of catalyst may be employed.

The reactor may be brought to the reaction temperature before or after the introduction of the reaction feed mixture. However, in a large-scale operation, it is preferred to carry out the process in a continuous manner, and in such a system, the recirculation of the unreacted olefin is contemplated.

The catalyst compositions and oxidation process of 5 EXAMPLES l-16 1. In a typical preparation of the unpromoted catalyst, 87.8 g of uranyl nitrate (U (NO .6l-l O were dissolved in about 100 cc of hot water; 154.3 g of orthoarsenic acid H AsO J/2 H O were dissolved in about 400 cc of hot water. The uranyl nitrate solution was added to the dilute ortho-arsenic acid and the mixture stirred. To this mixture was added 116.8 g of Ludox AS, a commercially available dispersion of 30 percent by weight of silica, SiO- The mixture was continuously heated with constant stirring until it gelled. The gel was spooned into trays, placed in an atmospheric convection oven at 120C and dried overnight. The oven-dried catalyst was then heat-treated in a furnace open to the atmosphere, starting at 800F and being raised to 900F over a period of about 2 hours. The catalyst was calcined overnight at 900F. The catalyst obtained had a composition which may be written as 82.5 percent UAs O 17.5 percent SiO 2. A portion of the above-described catalyst (calcined at 900F) was further calcined at 1,200F for 3.5

hours.

3. A portion of the above-described catalyst (calcined at 900F) was further calcined at 1,375F for 3 hours. 4. In another preparation of the unpromoted catalyst, 215 g of uranyl nitrate were dissolved in about 200 cc of hot water; 64.6 g of ortho-arsenic acid H AsO /z H O were dissolved in about 100 cc of hot water. The uranyl nitrate solution was added to the dilute orthoarsenic acid and the mixture stirred. To this mixture was added 116.8 g of Ludox AS a commercially available dispersion of 30 percent by weight of silica, SiO The mixture was continuously heated with constant stirring until it gelled. The gel was spooned into trays, placed in an atmospheric convection oven at 120C and dried overnight. The oven-dried catalyst was then heattreated in a furnace open to the atmosphere, starting at 800F and being raised to 900F over a period of about two hours. The catalyst was calcined overnight at 900F. The catalyst obtained had a composition which may be written as 82.5 percent UAsO 17.5 percent SiO 5. A portion of the above-described catalyst (calcined at 900F) was further calcined at 1,200F for 3.5 hours.

6. A portion of the above-described catalyst (calcined at 900F) was further calcined at 1,500F for 3 hours.

7. A portion of the above-described catalyst (calcined at 900F) was further calcined at 1,700F for 3 hours.

8. In another preparation of the unpromoted catalyst 239 g of uranyl nitrate (U0 (NO .6H O were dissolved in about 200 cc of hot water; 48.1 g of orthoarsenic acid H AsO /2 H O were dissolved in about cc of hot water. The uranyl nitrate solution was added to the dilute ortho-arsenic acid and the mixture stirred. To this mixture was added 1 16.8 g of Ludox AS, a commercially available dispersion of 30 percent by weight of silica, SiO The mixture was continuously heated with constant stirring until it gelled. The gel was spooned into trays, placed in an atmospheric convection oven at C and dried overnight. The oven-dried catalyst was then heat-treated in a furnace open to the atmosphere, starting at 800F and being raised to 900F over a period of about 2 hours. The catalyst was calcined overnight at 900F. The catalyst obtained had a composition which may be written as 82.5 percent UAS Q 17.5 percent SiO 9. A portion of the above-described catalyst (calcined at 900F) was further calcined at 1,200F for 3.25 hours.

10. A portion of the above-described catalyst (calcined at 900F) was further calcined at 1,500F for 3.5

hours.

1 1. A portion of the above-described catalyst (calcined at 900F) was further calcined at 1,750F for 3 hours.

Other catalyst compositions were prepared in a manner similar to that described hereinabove, so as to vary the ratio of arsenic to uranium. Ratios as low as 0.1 gave good conversions, though the better conversions were obtained with ratios in excess of 2.

Percent Conversion to Acrylonitrile Moles Acrylonitrile Recovered Moles Propylene Fed TABLE 1 Ex. No.

Atomic Ratio ArseniczUranium Unpromoted Catalyst Calcined Overnight at 900F & Additionally for Percent Per Pass Conversion of Propylene to Acrylonitrile ambush- TABLE I Continued Unpromoted Catalyst Calcined Over- Percent Per Pass The following Table II shows runs for the conversion of isobutylene to methacrylonitrile, made withsome of the above-described unpromoted catalysts, all the runs having been made under substantially similar process conditions those described for preceding Table l.

TABLE II The following Table IV shows runs, for the conversion of isobutylene to methacrylonitrile, make with some of the above-described promoted catalysts, all the runs having been made under substantially similar process conditions as those described for the preceding Unpromoted Catalyst Calcined Overnight Percent Per Pass Con- Ex Atomic Ratio at 900F and version Isobutylene No ArseniczUranium Additionally for to Methacrylonitrile 17 0.7 3 hrs. at 1500F 19.8 18 1 3.5 hrs. at 1200F 39.7 19 2 3 hrs. at 1700F 29.6 20 3 3 hrs. at 1200F 42.8 21 5.8 3 hrs. at 1375F 57.7

The following Table 111 shows runs. for the conversion of propylene to acrylonitrile, made with some of the above-described promoted catalysts, all the runs having been made under substantially similar process Table I. The promoted catalyst composition may be,

written M U; As O where M denotes the promoter element and values for the symbols a, and y are listed in the following Table IV. 7

TABLE IV Calcined Over- Percent Per Atomic Ratios night at 900F Pass Conversion Ex. of Components and Additionally of Propylene No. Promoter a x y for to Acrolein 33 Molybdel 1 0.25 3 hrs. at ll0OF 56.1

num 34 Molybde l 1 0.25 3 hrs. at 1000F 66.8*

num 35 Antimony l l 3 9.4 36 Vanadium 0.1 1 3 8.3

Molar Feed ratio of C;,=/nir/H 1/11/4 conditions as those described for preceding Table I. The promoted catalyst composition may be written M. U, As 0 where M denotes the promoter element and values for the symbols (1.x, and y are listed in the following Table 111.

TABLE III Calcined Over- The following Table V shows runs, for the conversion 50 of propylene to acrolein, made with some of the abovedescribed unpromoted and promoted catalysts, all the runs having been made under substantially similar process conditions as those described for preceding Table Percent Per Pass Atomic Ratios night at 900F Conversion of Ex. of Components and Additionally Propylene to No. Promoter a .t v for Acrylonitrile 22 Tungsten 0.1 l 3 3 hrs. at 1000F 48.2 23 Zinc 0.1 1 3 49.6 24 Manganese 0.1 1 3 52.1 25 Iron 0.1 l 3 53.4 26 Chromium 0.1 l 3 54.7 27 Bismuth 0.1 1 3 57.2 28 Nickel 0.1 1 3 59.7 29 Tin 0.1 l 3 60.1 30 Vanadium 0.1 l 3 61 31 Boron 0.1 l 3 61.1 32 Molybde 0.1 l 3 71.)

l. The promoted catalyst composition M U, As 0 where M denotes the promoter element and values for the symbols a, x and y are listed in the following Table V.

We claim:

1. A catalyst composition consisting essentially of a catalyst support supporting an activated catalytic oxide complex of arsenic and uranium having a composition TABLE V Percent Per Pass Conversion Calcined Over- Atomic Ratios night at 900F The following Table VI shows runs, for the conversion of isobutylene to methacrolein, made with some of the above-described unpromoted and promoted catalysts, all the runs having been made under substantially similar process conditions as those described for preceding Table l. The promoted catalyst composition may be written M U, As 0 where M denotes the promoter element and values for the symbols a, x and y are listed in Table VI below.

TABLE VI corresponding to the empirical chemical formula U, As 0 where x is a number from about 1 to about 25; y is a number within the range from about 1 to about 10; z is a number taken to satisfy the average valences of arsenic and uranium in the oxidation states in which they exist in said catalyst, said catalyst being formed by heating the mixed oxides of arsenic and uranium in the presence of oxygen at an elevated temperature above 500F but below their melting point for a time suffi- Calcined Overnight at 900F and Additionally for Atomic Ratios Ex. of Components Percent Per Pass Conversion of lsobutylene to No. Promoter a x y Methacrolein 44 None 1 0.7 3 hrs. at 900F 11.9 45 None 1 4.5 3 hrs. at 1000F 14.7 46 None l 5 3 hrs. at 1200F 18.8 47 Nickel l 1 3 3 hrs. at 1000F 31.9 48 Tin 0.5 l 3 3 hrs. at 1100F 29.8 49 Molybde- 1 l 3 39.8

num

The following Table VI] shows runs, for the conver- 45 cient to form said active catalytic oxide.

sion of l-butene to butadiene, made with some of the above-described promoted catalysts, all the runs having been made under substantially similar process conditions as those described under preceding Table I. The promoted catalyst composition may be written Mu ,U, As 0 where M denotes the promoter element and values for the symbols a, x and y are listed in the Table Vll below.

TABLE VI] 2. The catalyst composition of claim 1 wherein the catalyst support is silica.

3. A promoted catalyst composition consisting essentially of a base catalyst, a support and a promoter com- 50 ponent, said base catalyst comprising the oxides of arsenic and uranium, said support being silica and said promoter component comprising an oxide of at least one element selected from the group consisting of mo- Calcined Over- Atomic Ratios night at 900F Percent Per num valences of arsenic, uranium and the promoter element in the oxidation states in which they exist in the catalyst.

4. The promoted catalyst composition in accordance with claim 3, activated by heating at a temperature above 5()()F but below a temperature deleterious to the catalyst. 

1. A CATALYST COMPOSITON CONSISTING ESSENTIALLY OF A CATALYST SUPPORT SUPPORTING AN ACTIVATED CATALYTIC OXIDE COMPLEX OF ARSENIC AND URANIUM HAVING A COMPOSITION CORRESPONDING TO THE EMPIRICAL CHEMICAL FORMULA UZASYOZ WHERE X IS A NUMBER FROM ABOUT 1 TO ABOUT 25; Y IS A NUMBER WITHIN THE RANGE FROM ABOUT 1 TO ABOUT 10; Z IS A NUMBER TAKEN TO SATISFY THE AVERAGE VALENCES OF ARSENIC AND URANIUM IN THE OXIDATION STATES IN WHICH THEY EXIST IN SAID CATALYST, SAID CATALYST BEING FORMED BY HEATING THE MIXED OXIDES OF ARSENIC AND URANIUM IN THE PRESENCE OF OXYGEN AT AN ELEVATED TEMPERAURE AOVE 500*F BUT BELOW THEIR MELTING POINT FOR A TIME SUFFICIENT TO FORM SAID ACTIVE CATALYTIC OXIDE.
 2. The catalyst composition of claim 1 wherein the catalyst support is silica.
 3. A promoted catalyst composition consisting essentially of a base catalyst, a support and a promoter component, said base catalyst comprising the oxides of arsenic and uranium, said support being silica and said promoter component comprising an oxide of at least one element selected from the group consisting of molybdenum, boron, vanadium, tin, nickel, bismuth, chromium, iron, manganese, zinc, tungsten, antimony and cerium, said catalyst composition corresponding to the empirical formula Ma Ux ASy Oz wherein M denotes at least one promoter element; a is a number less than 1; x is a number within the range of from about 1 to about 25; y is a number within the range of from about 1 to about 10; and z is a number taken to satisfy the average valences of arsenic, uranium and the promoter element in the oxidation states in which they exist in the catalyst.
 4. The promoted catalyst composition in accordance with claim 3, activated by heating at a temperature above 500*F but below a temperature deleterious to the catalyst. 